Cutting beveled strip from center of board

[bmuir1616]

For some reason I cannot get this technique through my head:

How do I cut a bevel strip (30-degrees on each side) from the center of a 24-inch square piece of plywood so the top of the strip (top of the truncated pyramid end view) is 3/4" wide and the center of the board is down the middle of the 3/4" top of the strip?
Thanks, Bill

[pelligrini]

Fence placement will be critical. You will be flipping the offcut (wider) board over and rotating it 180 degrees as well.

[cabinetman]

For some reason I cannot get this technique through my head:

How do I cut a bevel strip (30-degrees on each side) from the center of a 24-inch square piece of plywood so the top of the strip (top of the truncated pyramid end view) is 3/4" wide and the center of the board is down the middle of the 3/4" top of the strip?
Thanks, Bill

You can see from your picture that both outside pieces after a cut has the same angle after both cuts. To get your center rib figured accurately, draw on the ends of the board the two angle lines creating the center rib angles. Set the angle of bevel for the blade. With the saw off, set the board against the fence behind the blade and sight the blade on your pencil lines.

Lets assume you have a left tilt saw (just for discussion). Set one edge against the fence and make your first cut with the center rib to be figured on the waste piece. Your first cut yields one board with the angle, and the waste piece has the complimentary angle. Turn it around and run the straight edge against the fence, but set the fence for the width needed for the rib. Make a pass.

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[gsmittle]

I wonder if there's a router bit that would work?

g.

[cabinetman]

I wonder if there's a router bit that would work?

g.

You would have to have one with the correct face angle, and a face length long enough to clear the stock. The downside is that it would remove too much stock in making a pass. Of course, you could cut the three pieces and edge them accordingly. Not a method I would use.

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[leehljp]

If you do not have the experience, I would cut the appropriate sides a little large and then use either a 30° router bit, or just cut the bevel on a TS for that particular side and for each of the larger pieces. Get a second piece of 3/4 ply about 6 to 8 inches wide and cut the bevel on one side. Then carefully place the fence the right distance away from the tilted saw blade and cut the center strip.

Now the reason I said that above is because you are obviously unsure. If you have only one piece of plywood the right size to begin with, you will more than likely mess it up. Don't feel bad about that. Many many professional furniture makers make a "mock-up" before attempting the real thing. And in your case, I am recommending that you don't attempt cutting the center strip out of one piece of ply if you cannot see it in your mind's eye. That is a mistake waiting to happen. Again, it is not you, it is your lack of experience and even professionals look for alternatives to prevent mistakes - that is the 2nd reason they do mockups . . . to find out what works well and what doesn't. A mockup gives practice and confidence and also shows where problems are likely to occur.

[LCHIEN]

I'm going to make some presumptions here.
One is that your design needs the center strip, and exactly 3/4" wide on the top, for something.. Second, that you are using the two wide offcuts to join together at the apex of a 60- degree angle. Thus its important that the top sides meet at the apex so the best appearance is given. Is it also important that the two wide offcuts be identical in size (width)?

If not there may be easier ways to cut this up.

But if its as I presume, then Pellegrini is right, you cut once, then flip and rotate. The most absolutely critical thing is the fence to blade distance. Any error in blade positioning becomes a double error in the width of the narrow bevel piece. And the width of the wide offcuts is a function of the blade kerf. Width is always difficult to measure and cut when a bevel is on one edge.

[woodturner]

If not there may be easier ways to cut this up.

Safer, too. From the notes on the drawing, this appears to be a bandsaw table, so grain doesn't matter.

I would do the following (see drawing)
1. Set the bevel on the blade and use the fence to bevel one edge of the plywood
2. Flip the plywood, set the fence over and cut the strip off the same edge of the plywood
3. Turn the plywood end for end, set the fence, and bevel the other edge.
4. Set the blade to 90 degrees, set the fence, and cut the plywood down the middle to make the two large pieces.

[capncarl]

I thought that bmuir1616 wanted the beveled strip out of the "center" of the board. (I can not see his attached photo, it is blocked). If the center strip is wanted, I'd locate the center of 24" board, mark off 3/8" to each side and set the saw to cut the outside of each mark @30 degrees. At least it is only a 2'x2' board, not a full 4x8 piece, easy enought to handle on a bt. Nothing was said about how much material was desired on each side of the bevel cut, but it must have been optional.
capncarl

[woodturner]

I thought that bmuir1616 wanted the beveled strip out of the "center" of the board.

That's what he said in the post, but the drawing posted suggests the project is a bandsaw table with a dovetailed miter slot, so it appears it does not actually have to be cut from the center of the piece of plywood.

[pelligrini]

Safer, too. From the notes on the drawing, this appears to be a bandsaw table, so grain doesn't matter.

I would do the following (see drawing)
1. Set the bevel on the blade and use the fence to bevel one edge of the plywood
2. Flip the plywood, set the fence over and cut the strip off the same edge of the plywood
3. Turn the plywood end for end, set the fence, and bevel the other edge.
4. Set the blade to 90 degrees, set the fence, and cut the plywood down the middle to make the two large pieces.

I really don't think the method you have pictured is any safer at all. The cut in the 3rd step is extremely unsafe. One should never run a bevel like that at the bottom of the rip fence. If it should slide under a portion of the rip fence the piece could bind and get trapped under the tilted blade. The results could be disastrous. It can also result in an uneven bevel, which doesn't work well when fabricating moving parts.

With proper fence placement the 3/4" sliding piece could be cut out of one piece of plywood with one fence setup and just two passes. You would end up with two larger pieces of the same dimensions and the trapezoidal slider.

I'd mark it like cabinetman and capncarl suggested, and align the rip fence so I'd be cutting the first outside edge of the sliding tongue. I usually align a blade tooth edge to my line. Make the first pass and you would have the first half of your table. Flip the board over, and rotate it 180 degrees and make the second pass. The offcut will be your sliding tongue.

I'm not sure how their recommendation of adding 2" to the saw table side depth works, unless there are some additional trimming and fitting cuts, or if the top sticks over the bandsaw top for some edging to be added below.

[cabinetman]

I really don't think the method you have pictured is any safer at all. The cut in the 3rd step is extremely unsafe. One should never run a bevel like that at the bottom of the rip fence. If it should slide under a portion of the rip fence the piece could bind and get trapped under the tilted blade. The results could be disastrous. It can also result in an uneven bevel, which doesn't work well when fabricating moving parts.

I agree. I wouldn't put your money (or mine) on getting a nice, even, flat bevel with using a bandsaw in the first place.

I'd mark it like cabinetman and capncarl suggested, and align the rip fence so I'd be cutting the first outside edge of the sliding tongue. I usually align a blade tooth edge to my line. Make the first pass and you would have the first half of your table. Flip the board over, and rotate it 180 degrees and make the second pass. The offcut will be your sliding tongue.

I took my meds and maybe all my neurons aren't touching, but the way I described the cut on the tablesaw, I don't see the piece being flipped and rotated. With the bevel set on the first cut, you can see the bevel in relation to the board. By just turning the waste piece (which contains the rib section) making the same cut (to get the rib piece) is the same pass as the first pass (without flipping it). Did I OD with my meds?

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[woodturner]

I really don't think the method you have pictured is any safer at all. The cut in the 3rd step is extremely unsafe. One should never run a bevel like that at the bottom of the rip fence. If it should slide under a portion of the rip fence the piece could bind and get trapped under the tilted blade.

If the fence is a stock fence with a gap under it, I agree, it could be questionable.

I use (and assumed most people do) a wood auxiliary fence that is adjusted to be in contact with the table. The fence prevents the piece from sliding under the fence, making for a very safe cut.

Alternatively, you could cut with the piece bevel down, so that the part touching the blade is the thickness of the plywood above the table.

The danger with making these cuts on a conventional table saw, with a right-tilt blade, is that it is less safe to cut the bevel up and between the fence and the blade, as the blade can pinch the cut and cause a kickback. Ideally, the fence would be moved to the left side of the blade, but not all table saws have a large enough table and rails to accommodate that. Without that option, the sequence suggested is safer because it minimizes the "trapped" cuts.

Alternatively, cut the strip off the edge, leaving one edge of the plywood beveled, reset the blade to vertical, cut the pieces in half, then reset the bevel and cut the bevel on the final piece. The problem with this method is that the blade must be moved, which decreases accuracy.

In the original plans, it appears the motivation for cutting the strip from the middle is to increase accuracy and consistency of the bevel. It can be done with one blade setting and two cuts, but the strip width will be harder to control accurately.

As always, what is the "best" method for a particular person will depend on their skills, tools, and comfort level.

[pelligrini]

Yea, cabinetman, it does just get turned around. If It were flipped and turned you'd end up with a parallelagram section. I kept seeing the bevel direction of the slider offcut.

[Carpenter96]

Bevel

You could use a simple piece of 1/4" hard board or plywood to make sure the bevel does not slip under the fence, we do it all the time with plastic laminates. It also acts as a zero clearance for the blade. Regards Bob